Western blot analysis of extracts from WI-38 cells, serum-starved for 3 days (-) or serum-starved for 3 days followed by treatment with 10% serum for 2 days (+), using Phospho-Rb (Ser807/811) (D20B12) XP® Rabbit mAb.

Immunoprecipitation of phospho-Rb (Ser807/811) from MCF7 cell extracts using Phospho-Rb (Ser807/811) (D20B12) XP® Rabbit mAb (lane 2). Western blot was performed using the same antibody. Lane 1 is 10% input.

Western blot analysis of extracts from WI-38 cells, serum-starved for 3 days (-) or serum-starved for 3 days followed by treatment with 10% serum for 2 days (+), using Phospho-Rb (Ser807/811) (D20B12) XP® Rabbit mAb.

Immunoprecipitation of phospho-Rb (Ser807/811) from MCF7 cell extracts using Phospho-Rb (Ser807/811) (D20B12) XP® Rabbit mAb (lane 2). Western blot was performed using the same antibody. Lane 1 is 10% input.

B. Protein Blotting

A general protocol for sample preparation.

Lyse cells by adding 1X SDS sample buffer (100 µl per well of 6-well plate or 500 µl for a 10 cm diameter plate). Immediately scrape the cells off the plate and transfer the extract to a microcentrifuge tube. Keep on ice.

Western Blot Reprobing Protocol

Reprobing of an existing membrane is a convenient means to immunoblot for multiple proteins independently when only a limited amount of sample is available. It should be noted that for the best possible results a fresh blot is always recommended. Reprobing can be a valuable method but with each reprobing of a blot there is potential for increased background signal. Additionally, it is recommended that you verify the removal of the first antibody complex prior to reprobing so that signal attributed to binding of the new antibody is not leftover signal from the first immunoblotting experiment. This can be done by re-exposing the blot to ECL reagents and making sure there is no signal prior to adding the next primary antibody.

(Optional) To assure that the original signal is removed, wash membrane twice for 5 min each with 10 ml of TBST. Incubate membrane with LumiGLO® with gentle agitation for 1 min at room temperature. Drain membrane of excess developing solution. Do not let dry. Wrap in plastic wrap and expose to x-ray film.

Wash membrane again four times for 5 min each in TBST.

The membrane is now ready to reuse. Start detection at the "Membrane Blocking and Antibody Incubations" step in the Western Immunoblotting Protocol.

B. Fixation

Collect cells by centrifugation and aspirate supernatant.

Resuspend cells in 0.5–1 ml 1X PBS. Add formaldehyde to obtain a final concentration of 4%.

Fix for 10 min at 37°C.

Chill tubes on ice for 1 min.

For extracellular staining with antibodies that do not require permeabilization, proceed to immunostaining (Section D) or store cells in PBS with 0.1% sodium azide at 4°C; for intracellular staining, proceed to permeabilization (Section C).

C. Permeabilization

NOTE: This step is critical for many CST antibodies.

Permeabilize cells by adding ice-cold 100% methanol slowly to pre-chilled cells, while gently vortexing, to a final concentration of 90% methanol. Alternatively, remove fix prior to permeabilization by centrifugation and resuspend in 90% methanol as described above.

Incubate 30 min on ice.

Proceed with immunostaining (Section D) or store cells at -20°C in 90% methanol.

D. Immunostaining

NOTE: Account for isotype matched controls for monoclonal antibodies or species matched IgG for polyclonal antibodies. Count cells using a hemocytometer or alternative method.

Aliquot 0.5–1 x 106 cells into each assay tube (by volume).

Add 2–3 ml incubation buffer to each tube and wash by centrifugation. Repeat.

Specificity / Sensitivity

Phospho-Rb (Ser807/811) (D20B12) XP® Rabbit mAb recognizes endogenous levels of Rb protein only when phosphorylated at Ser807, Ser811, or at both sites. This antibody does not cross-react with Rb phosphorylated at Ser608.

Source / Purification

Background

The retinoblastoma tumor suppressor protein Rb regulates cell proliferation by controlling progression through the restriction point within the G1-phase of the cell cycle (1). Rb has three functionally distinct binding domains and interacts with critical regulatory proteins including the E2F family of transcription factors, c-Abl tyrosine kinase, and proteins with a conserved LXCXE motif (2-4). Cell cycle-dependent phosphorylation by a CDK inhibits Rb target binding and allows cell cycle progression (5). Rb inactivation and subsequent cell cycle progression likely requires an initial phosphorylation by cyclin D-CDK4/6 followed by cyclin E-CDK2 phosphorylation (6). Specificity of different CDK/cyclin complexes has been observed in vitro (6-8) and cyclin D1 is required for Ser780 phosphorylation in vivo (9).

Data Sheets & Documentation

For Research Use Only. Not For Use In Diagnostic Procedures.
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